Comply with JC Specification

[mavroudisv]

Since JCMathLib implements some classes from the specification (int, BigNumber) it would be useful to fully comply with it, whenever possible.

In most cases, we provide additional functionality and that's ok.
I'm planning to do two things:

• Make sure that we provide all the methods found on the specification and we have the same signature.
• Rename classes and methods to match those of the spec.

This will temporarily hurt backwards compatibility, but in the long run will makes things easier, especially in cases where some of these classes start to appear in commercial cards.